1. Field of the Invention
The invention relates to a novel process for the manufacture of very low molecular weight polyphenylene ether resin, typically within the intrinsic viscosity range of about 0.08 dl/g to about 0.16 dl/g as measured in chloroform at 25.degree. C.
The invention also relates to the polyphenylene ether resin made by the process as well as blends and articles containing the polyphenylene ether resin made by the process.
2. Brief Description of the Related Art
Polyphenylene ether resins (hereinafter "PPE") are commercially attractive materials because of their unique combination of physical, chemical, and electrical properties. Furthermore, the combination of PPE with other resins provides blends which result in additional overall properties such as chemical resistance, high strength, and high flow.
The processes most generally used to produce PPE involve the self-condensation of at least one monovalent phenol in the presence of an oxygen containing gas and a catalyst comprising a metal amine complex to produce resins typically within the intrinsic viscosity range of about 0.35 dl/g to about 0.65 dl/g as measured in chloroform at 25.degree. C.
These processes are typically carried out in the presence of an organic solvent and the reaction is usually terminated by removal of the catalyst from the reaction mixture. The catalyst metal, after being converted into a soluble metal complex with the aid of a chelating agent, is removed from the polymer solution with standard extraction techniques, such as liquid-liquid extraction. The PPE polymer can be isolated in a variety of methods although generally by anti-solvent precipitation.
As new commercial applications are sought for PPE, a wider range of intrinsic viscosity resins, especially lower intrinsic viscosity resins, have been desired. As intrinsic viscosity decreases in PPE resins, the level of hydroxyl groups increases and the rheological properties change dramatically (lower viscosity as intrinsic viscosity decreases) as compared to current commercially available high molecular weight PPE produced by the methods previously described. The physical properties of PPE remain highly desirable and sought after in applications such as, for example, adhesives, sealants and gels based on SBC, SBR, or epoxies for automotive, housing, cabeling, membranes and electrical applications. Also, epoxy based composites for aerospace, automotive structural members and sporting equipment are desirable applications as are electrical laminates, and IC encapsulation materials based on epoxies and unsaturated polyesters. Friction materials and abrasives compounds based on phenolic are also sought after. PPE is also useful as an additive in various thermoplastic and thermoset materials including, e.g., polypropylene, polystyrene, ABS, polycarbonate, polyetherimide, polyamides, polyesters, and the like and also thermosetting resins such as, for example, epoxies, unsaturated polyesters, polyurethanes, allylic thermosets, bismaleimides, phenolic resins, and the like. Varying enhanced properties may be improved in different systems such as, for example, improved heat performance, flame retardancy improvement, decrease of electrical properties like D.sub.k and D.sub.f, decrease in moisture absorption, increased creep resistance, thermal expansion reduction, chemical resistance to acids and bases, for various applications such as, for example, automotive and house hold and electrical goods.
It is therefore apparent that a need exists for the development of processes for the manufacture of very low molecular weight polyphenylene ether resin, typically within the intrinsic viscosity range of about 0.08 dl/g to about 0.16 dl/g as measured in chloroform at 25.degree. C.